1. Field of the Invention
The present invention concerns a method for rendering waterproof a roller compacted concrete or rubble hydraulic structure steeply sloped on the upstream side (of the step wall type).
2. The Prior Art
For economic reasons hydraulic structures such as dams tend to be made nowadays of roller compacted concrete. The building of roller compacted concrete dams is the object of numerous publications and in particular of a communication of ACI Committee 207 published in ACI Journal (1980, July-August, pp. 215-235).
However, it appears that roller compacted concrete dams may show excessive permeability to water, especially at the interfaces between successive layers. In the long term this may lead to the cement in the concrete being attacked, especially where the water is chemically aggressive.
To remedy this disadvantage there have previously been proposed numerous ways to render the side of such structures in contact with the water impermeable.
One proposal (Concrete International 1964, May, p. 42, ENR 1983, 24 February, p. 35) is to cover this side with vertical prefabricated concrete members bolted into the core. The effectiveness of this technique is limited by the service life of the fixtures, however. It is also difficult to seal the joints when using this technique, especially the horizontal joints.
Another proposal (Highway & Heavy Construction, 1985, January, p. 39) is to cover this side with a layer of ordinary concrete. However, this concrete is subject to cracking which is accentuated by the absence of shrinkage joints. Given that it is relatively thin, this facing is also subjected to high gradient percolation which is all the more damaging where the water retained by the hydraulic structure is chemically aggressive.
It has also been proposed (Concrete International 1983, March, p. 21) to cover this side with stainless steel, but a solution of this kind is extremely costly.
Finally, it has been proposed to render the surface impermeable by applying to it a continuous reinforced butyl rubber membrane (ibid, FIG. 3). The manufacture, installation and securing of a continuous membrane of this kind raise serious problems and this solution has been proposed for illustrative purposes only.